The present invention relates to an oil distribution system for an internal combustion engine. More specifically, the invention relates to an oil distribution system for a direct fuel injected (DFI) internal combustion engine that deposits oil in specific locations such that the reciprocating movement of the internal engine components distributes the oil.
In most fuel injected engines, the reciprocating movement of the pistons creates a vacuum inside the crankcase that draws air into the crankcase through a reed valve assembly. The fuel required for combustion is injected in a fine mist into the air flowing into the crankcase. In these engines, lubricating oil is combined with the fuel upstream from the reed valve assembly. The oil/fuel mixture forms a fine mist that is distributed into the crankcase under pressure. As each of the engine pistons moves in its cylinder, the piston creates a pressure that pushes the fine mist from the crankcase into the combustion chamber, where a spark plug ignites the fuel to power the engine. Since the lubricating oil is distributed along with the fuel, the oil/fuel mixture in the crankcase coats the crank shaft, the connecting rods, the underside of the piston heads and the other internal engine components that are in communication with the crankcase to provide adequate lubrication for the entire engine, particularly the bearings joining each connecting rod to one of the pistons and the crankshaft. This type of oil lubrication system is well known and has been used for many years to provide adequate lubrication for an internal combustion engine.
Recently, internal combustion engines have been developed incorporating direct fuel injection (DFI). In a DFI engine, fuel is introduced along with high pressure air directly into the combustion chamber of each cylinder after the exhaust port closes. The development of DFI engines has been driven by the need to meet ever increasing pollution standards, since a DFI system dramatically reduces the amount of unburned fuel entering the exhaust system and eventually draining into the water, in marine applications. Specifically, the underlying principle of introducing fuel directly into the combustion chamber greatly reduces the amount of pollution generated by a DFI engine, since a greater percentage of the fuel introduced into the combustion chamber is burned such that little or no unburned fuel escapes through the exhaust ports during each stroke of the engine. However, since fuel is no longer introduced into the crankcase under pressure, lubricating oil can no longer be introduced into the crankcase along with the fuel in a fine mist. Thus, problems arise in providing adequate lubrication for the rapidly moving internal engine components in a DFI engine.
In currently available DFI engines, oil is typically introduced along with air into the crankcase at a location downstream from the reed valve assembly. In this type of configuration, an oil pump distributes the oil in the air in an attempt to provide lubrication for the engine components, including the bearings between the connecting rods, the crankshaft, and the pistons. The lubricating oil is not efficiently dispersed within the engine block to provide the required amount of lubrication for the internal engine components.
In addition, when a DFI engine is used in a marine outboard motor, the engine block is typically mounted such that the crankshaft is oriented along a vertical axis and the pistons reciprocate in a generally horizontal plane. When lubricating oil is introduced into the crankcase downstream from the reed valve assembly, the oil has a tendency to be drawn by gravity toward the bottom of the crankcase. Thus, only a relatively small amount of oil contacts the wrist pin between the connecting rod and the piston head. Additionally, the oil lubrication system in a conventional DFI engine oftentimes provides inadequate lubrication for the bearings between the connecting rod and the crankshaft.
Therefore, it can be appreciated that an improved oil distribution system for an internal combustion engine that provides adequate distribution of oil on all of the internal engine components would be a desirable improvement. Specifically, an oil distribution system that can be used on a DFI engine to efficiently distribute oil in the required locations would be particularly desirable.